I've done mine using a product called Aluminex. I basically just used a spray bottle and then rinsed off. It works okay at best. I mean It will get the stuff off, it's acid based I'm sure. But it runs and leaves streaks etc. Not sure if anyone has used this or a combo of this and something else? What is everyone using? Here are some pictures where you can see where I ran out of the stuff and the difference it makes and also the streaks or spots that are hard to get because of the nature of the product application.
Before picture:
After picture using a spray bottle and a car wash